A wing and tail are geometrically similar, while tail area is one-third of the wing area and distance between two aerodynamic centres is equal to wing semi-span (b/2). In addition, following data is applicable: ε_a = 0.3, C_L = 1.0, C_Lα = 0.08/deg., ¯c = 2.5 m, b = 30 m, C_Mα = 0, η_t = 1. The symbols have their usual aerodynamic interpretation.
The maximum distance that the centre of gravity can be behind aerodynamic centre without destabilizing the wing-tail combination is